For effective utilization of a combustible gas as a fuel or the like, it is necessary to enrich the combustible gas to an appropriate range by separating gas such as air from the source gas containing this combustible gas. Various apparatuses and methods have been proposed for enrichment of such combustible gas. For instance, Patent Document 1 discloses an invention in which a gas (the so-called coal mine gas) generated from a coal mine and containing methane gas as a combustible gas is employed as a source gas and air (containing mainly, nitrogen, oxygen and carbon dioxide) is separated from this source gas with using an adsorbent, thus enriching the methane gas for its utilization.
More particularly, the combustible gas enrichment system disclosed in Patent Document 1 includes an adsorption unit charged therein with an adsorbent for selectively adsorbing the combustible gas, a source gas feeding means capable of feeding source gas into an adsorption unit from the outside, and a suctioning means capable of suctioning the gas from the inside of the adsorption unit. And, the system effects an adsorption process for feeding the source gas into the adsorption unit by the source gas feeding means for adsorption of the combustible gas to the adsorbent and a desorption process for desorbing the combustible gas from the adsorbent under the suction force of the suctioning means after the adsorption process and taking the desorbed combustible gas to the outside. As the suctioning means described above, there is employed a vacuum pump device comprised of a pump and a drive motor for driving this pump.